Communication apparatus



I- 14, 1945- o. A. SHANN 2,381,986

COMMUNICATION APPARATUS Filed Oct. 24, 1942 2 Sheets-Sheet 1 FIG.

INVENTOR 0. A. SHANN BY 1 Z Z ATTORNEY Aug. 14, 1945. Q A SHANN 2,381,986

7 COMMUNICATION APPARATUS Filed 001:. 24, 1942 2 Shets-Sheet 2 EXTENSION STAT/0N FIG. 6

. I /N VE N TOR Rsconomc By 0. A. SHA/V/V DEV/CE Patented Aug. 14, 1945 COMMUNICATION APPARATUS Oscar A. Shann, Short Hills, N. J., asslgnor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 24, 1942, Serial No. 463,171

6 Claims. (01. 179-81) This invention relates to communication apparatus and particularly to telephone substation devices.

The object of the invention is to provide means responsive to a simple manipulation of the substation instrument whereby a subscriber may establish a given circuit condition such as to change the transmission characteristics of his station, to signal an assistant or to connect a monitoring instrument to his circuit. Almost from the beginning of the use of the telephone it has been a habit of the telephone user to jiggle his receiver hook when he found difliculty in making himself heard. The efiort is, of course, to attract the attention of the operator whereupon the dimculty may be stated and remedied. This habit of quickly manipulating the switchhook has carried over into the machine switching field but of course is ineifectual there as no operator's attention may be attracted. It is, therefore, the object of the present invention to automatically improve the transmission characteristics of a substation telephone in response to the manipulation of the switchhook during use of such instrument.

This same operation may be employed to signal an assistant, to connect a monitoring instrument to the circuit, or to perform any other useful function such as to turn off a radio set.

In accordance with this invention an amplifier is provided in the substation circuit but is normally out of circuit and ineffective. In addition a device which is cumulatively responsive to pulses of current created by rapid manipulation of the switchhook is provided which upon respouse will switch such amplifier in circuit. In accordance with the preferred embodiment of the invention a thermistor is provided which is effectually in circuit only during the movement of the switchhook. This device in response to a. small current flow therethrough will change its electrical resistance from a high to a low value so that if the switchhook is rapidly manipulated several times the resistance of the thermistor will change to a point where a relay in circuit therewith may be operated. The relay upon operation will switch the amplifier in circuit and lock in its operated position until the use of the substation instrument is terminated.

In accordance with other embodiments of this invention the thermistor and relay circuit may be employed for other useful purposes. A simple signal may be displayed before an assistant who may in this manner be summoned, or such a signal may be displayed alongside an assistants extension instrument so that he may be thus directed to listen in" on the conversation, or such a signal may be displayed and a monitoring connection may be established so that an assistant may listen in on the conversation, or a mechanical recording instrument may be connected to the line so that a record of the ensuing conversation may be made.

A feature of the invention is a means in a telephone responsive to rapid manipulation of the switchhook thereat for operating a relay to perform any one of a number of useful functions.

Another feature is a means in a telephone cumulatively responsive to current surges for operating a relay to perform any one of a number of useful functions.

Another feature of the invention. is a relay in a telephone circuit unresponsive to either the normal open or closed circuit thereof but responsive to the rapid manipulation of the switchhook. Such a relay is in a self-locking circuit and once energized will remain in that condition responsive to the normal closed condition of the telephone circuit.

Another feature of the invention is a thermistor eflectively in circuit only during the movement of the switchhook.

Still another feature is a thermistor and a relay in a normally ineffective circuit which is rendered effective by the change in resistance of the thermistor in response to the rapid manipulation of the switchhook.

Another feature of the invention is a means in a telephone responsive to rapid manipulation of the switchhook for effecting improved transmission thereover.

The drawings consist of two sheets having six figures, as follows:

Fig. 1 is a circuit diagram of a telephone substation circuit in conditionfor use but with the mechanical amplifier outzof circuit;

Fig. 2 is a fragmentary view illustrating the method of bringing the mechanical amplifier into circuit, showing how the switchhook may be rapidly manipulated and the condition of the switchhook contacts that will set up the required circuit conditions;

Fig. 3 is a circuit diagram similar to that of Fig. 1 showing the mechanical amplifier effectively included in the circuit;

Fig. 4 is a circuit diagram, schematic in part, showing how a signal may be displayed alongside an assistant's extension station either to summon in on the conversation;

Fig. is another circuit diagram, schematic in part, showing how a monitoring receiver may be connected to the telephone circuit; and 1 tion. The transmitter current flows from the.

tip conductor T, over contacts 3, 2 and I of the switchhook 6, contacts I and 2 of the dial 1, transmitter 8 of handset 9, the right-hand winding or induction coil III to the ring conductor R. The receiver II is in a local circuit including the receiver I I, the lower half of the left-hand winding of induction coil I0, contacts 6 and 5 of dial I, contact I and armature of relays I2, contacts 4 and 5 of switchhook 3 to receiver II.

The mechanical amplifier consisting of coil I3, diaphragm I4 and microphone I5 is not in circuit since contact 3 of relay I2 is open at this time. The relay I2 cannot be operated since the closure 0! contact 2 to contact 3 of the switchhook places this relay in a circuit which does not include any source or current.

, However, if the switchhook is "jiggled the condition depicted in Fig. 2 is set up once on the is connected to the line conductors T and B. so as to notify the assistant to listen in on the conversation. Alternatively, it may simply be used to summon an assistant.

In Fig. 5 the relay I2 may be used to signal an assistant and at the same time to connect a monitoring device, such as a receiver I9, to the telephone line. In such an arrangement the monitoring device may only be rendered efl'ective at the will of the subscriber.

In Fig. 6 the monitoring device of Fig. 5 is replaced by a mechanical recording device 20, such as a telegraphone for making a reproducible record of the conversation.

What is claimed is:

1. In a communication system, a station circuit'equipped with a switch for placing said cirdownstroke and once on the upstroke of the switchhook plunger 6. The contacts I, 2 and 3 are arranged so that contact is made between contacts ,I and 2 before contact 3 is closed to contact 2. At this time a circuit may be traced from tip conductor T, contacts 4 and 5 of relay I2, winding of relay I2, thermistor I6, contacts 2 and I of switchhook B and thence over the transmitter circuit previously traced. Thus if the switchhook is rapidly manipulated there will be a train of current impulses fed through the thermistor I6 and relay I2. The thermistor I5 is a well-known device which is normally of very high resistance. However, the heating effect of a current flow therethrough results in a change to a comparatively low resistance. Hence in comparatively short time the current flow through relay I2 rises to a point suflicient to operate this relay which thereupon locks in a local circuit which is maintained thereafter until the use of the circuit is given up and the handset returned to its cradle. The local circuit for maintaining relay I2 energized is shown in Fig. 3 and may be traced from relay I2, through thermistor I8 which is now maintained at a comparatively low resistance, contacts 2 and 3 of switchhook 6, battery I1, contacts 6 and 5 of relay I2 and thence to relay I2. The coil I3 of the mechanical amplifier is now in circuit with the lower half of the left-hand winding of induction coil III and by responding to incoming voice currents will, through microphone button I5, cause an increased or amplified response in the receiver II.

In Fig. 4 relay I2, besides operating its looking contacts, now closes a contact to operate a signal, such as a lamp IT. This may be placed near an assistants extension station I8 which cuit in condition for service, an auxiliary station circuit, a relay for rendering said auxiliary circuit efl'ective and a thermistor responsive to the repeated rapid manipulation of said switch for operating said relay.

2. In a communication system, a station equipped with transmission means, means for changing the characteristics of said transmission means, a switch for placing said station in condition for service, and means including a thermistor responsive to the repeated rapid manipulation of said switch for rendering said amplifying means effective.

3. In a communication system, a station equipped with signal receiving and transmitting means, a signal amplifier, a switch for placing said station in condition for service, and means including a thermistor responsive to the repeated rapid manipulation of said switch for rendering said amplifier efiective.

4. In a communication system, a station equipped with signal receiving and transmitting means, a signal amplifier, a switch for placing said station in condition for service, a relay for eflfectively placing said amplifier in service, a thermistor, contacts controlled by said switch 'for transiently energizing said thermistor during movement of said switch between its on and off positions, said relay being responsive to said thermistor.

5. In a communication system, a station equipped with signal receiving and transmitting means, a signal amplifier, a switch for placing said station in condition for service, a relay for efiectively placing said amplifier in service, a thermistor, contacts controlled by said switch for transiently energizing said thermistor during movement of said switch between its on and oil positions, said relay being responsive to said'thermistor, and a locking circuit for said relay for holding said amplifier in circuit after an initial operation of said relay.

6. In a communication system, a station circuit equipped with a switch for placing said circuit in condition for service, an auxiliary circuit at said station, means controlled by said switch for creating a local impulse during the movement thereof and means responsive to a train of local impulses created by the repeated rapid manipulation of said switch for rendering said auxiliary circuit effective.

OSCAR A. SHANN. 

